KR102546177B1 - Apparatus and method for managing connection in wireless communication system - Google Patents

Abstract

The present disclosure relates to a ^5th generation (5G) or pre-5G communication system for supporting a higher data transmission rate after a ^4th generation (4G) communication system such as Long Term Evolution (LTE). The present disclosure is for managing a connection in a wireless communication system, and a method of operating a distribution unit of a base station includes a process of receiving a first control message processed by a central unit from a terminal, and a request by the first control message sending a modified first control message to the central unit to indicate rejection of the procedure; and receiving, as a response to the modified first control message, a second control message indicating rejection of the procedure. process may be included.

Description

APPARATUS AND METHOD FOR MANAGING CONNECTION IN WIRELESS COMMUNICATION SYSTEM}

[0002] This disclosure relates generally to wireless communication systems, and more specifically to apparatus and methods for managing connections in wireless communication systems.

Efforts are being made to develop an improved 5th generation ( ^5G ) communication system or ^a pre-5G communication system in order to meet the growing demand for wireless data traffic after the commercialization of a 4th generation (4G) communication system. For this reason, the 5G communication system or pre-5G communication system has been called a Beyond 4G Network communication system or a Post LTE system.

In order to achieve a high data transmission rate, a 5G communication system is being considered for implementation in a mmWave band (eg, a 60 gigabyte (60 GHz) band). In order to mitigate the path loss of radio waves and increase the propagation distance of radio waves in the ultra-high frequency band, beamforming, massive MIMO, and Full Dimensional MIMO (FD-MIMO) are used in 5G communication systems. ), array antenna, analog beam-forming, and large scale antenna technologies are being discussed.

In addition, to improve the network of the system, in the 5G communication system, an evolved small cell, an advanced small cell, a cloud radio access network (cloud RAN), and an ultra-dense network , Device to Device communication (D2D), wireless backhaul, moving network, cooperative communication, CoMP (Coordinated Multi-Points), and reception interference cancellation etc. are being developed.

In addition, in the 5G system, Advanced Coding Modulation (ACM) methods such as FQAM (Hybrid Frequency Shift Keying and Quadrature Amplitude Modulation) and SWSC (Sliding Window Superposition Coding) and advanced access technology FBMC (Filter Bank Multi Carrier) ), Non Orthogonal Multiple Access (NOMA), and Sparse Code Multiple Access (SCMA) are being developed.

In the 5G system, various network structures are being discussed to improve system operation efficiency. For example, network virtualization, a split of a base station into a central unit (CU) and a distributed unit (DU), and the like are being discussed. Accordingly, it is necessary to further study an operation method suitable for a new network structure.

Based on the above discussion, the present disclosure provides an apparatus and method for efficiently managing a connection in a wireless communication system.

In addition, the present disclosure provides an apparatus and method for managing a connection in an environment in which a base station is divided into a central unit (CU) and a distributed unit (DU) in a wireless communication system.

In addition, the present disclosure provides an apparatus and method for processing a control message according to resource status in a distribution unit of a base station in a wireless communication system.

According to various embodiments of the present disclosure, a method of operating a distributed unit of a base station in a wireless communication system includes a process of receiving a first control message processed by a central unit from a terminal, and a process requested by the first control message sending a modified first control message to the central unit to indicate rejection of the procedure, and receiving, as a response to the modified first control message, a second control message indicating rejection of the procedure. can include

According to various embodiments of the present disclosure, a method of operating a central unit of a base station in a wireless communication system includes receiving a first control message generated by a terminal from a distribution unit, and the first control message is sent to the first control In response to confirming that the procedure requested by the message is modified to indicate rejection, transmitting a second control message indicating rejection of the procedure.

According to various embodiments of the present disclosure, a method of operating a distribution unit of a base station in a wireless communication system includes receiving a first control message processed by a central unit from a terminal, and sending the first control message to the central unit. In response to the process of transmitting, receiving a second control message indicating the progress of the procedure as a response to the first control message, and determining that the procedure requested by the first control message is rejected, It may include dropping the second control message and sending a third control message corresponding to rejection of the procedure to the central unit.

According to various embodiments of the present disclosure, a distribution unit device of a base station in a wireless communication system may include a transceiver for transmitting and receiving signals, and at least one processor for controlling the transceiver. The transmitting and receiving unit receives a first control message processed by the central unit from a terminal, and transmits a modified first control message to the central unit to indicate rejection of a procedure requested by the first control message, As a response to the modified first control message, a second control message indicating rejection of the procedure may be received.

According to various embodiments of the present disclosure, a central unit device of a base station in a wireless communication system may include a transceiver for transmitting and receiving signals, and at least one processor controlling the transceiver. The transmitting and receiving unit receives the first control message generated by the terminal from the distribution unit and confirms that the first control message is modified to indicate that the procedure requested by the first control message is rejected, the procedure A second control message indicating rejection may be transmitted.

According to various embodiments of the present disclosure, a distribution unit device of a base station in a wireless communication system may include a transceiver for transmitting and receiving signals, and at least one processor for controlling the transceiver. The at least one processor receives a first control message processed by the central unit from a terminal, transmits the first control message to the central unit, and, as a response to the first control message, proceeds with the procedure. In response to receiving a second control message indicating a , and determining that the procedure requested by the first control message is rejected, the second control message is dropped, and a third control message corresponding to the denial of the procedure is sent. It can be controlled to transmit to the central unit.

An apparatus and method according to various embodiments of the present disclosure may efficiently manage a connection by processing a control message according to a resource status in a distribution unit of a base station.

Effects obtainable in the present disclosure are not limited to the effects mentioned above, and other effects not mentioned may be clearly understood by those skilled in the art from the description below. will be.

1 illustrates a wireless communication system according to various embodiments of the present disclosure.
2 illustrates a protocol stack of a terminal and a base station in a wireless communication system according to various embodiments of the present disclosure.
3 illustrates a configuration of a distributed unit (DU) of a base station in a wireless communication system according to various embodiments of the present disclosure.
4 illustrates a configuration of a central unit (CU) of a base station in a wireless communication system according to various embodiments of the present disclosure.
5 illustrates a configuration of a terminal in a wireless communication system according to various embodiments of the present disclosure.
6 illustrates a configuration of a communication unit in a wireless communication system according to various embodiments of the present disclosure.
FIG. 7 illustrates a signal exchange diagram when a context search succeeds during a radio resource control (RRC) state transition in a wireless communication system according to various embodiments of the present disclosure.
8 illustrates a signal exchange diagram when context search fails during RRC state transition in a wireless communication system according to various embodiments of the present disclosure.
9 illustrates a signal exchange diagram when an RRC state transition attempt is rejected in a wireless communication system according to various embodiments of the present disclosure.
10 is a flowchart for rejecting a state transition prior to transmission of a control message of a distribution unit of a base station in a wireless communication system according to various embodiments of the present disclosure.
11 illustrates a flowchart of a central unit of a base station in a wireless communication system according to various embodiments of the present disclosure.
12A illustrates a signal exchange diagram when a state transition attempt using an RRC resume procedure succeeds in a wireless communication system according to various embodiments of the present disclosure.
12B illustrates a signal exchange diagram when a state transition attempt using an RRC resume procedure is rejected by a distributed unit before delivery of a control message in a wireless communication system according to various embodiments of the present disclosure.
13A illustrates a signal exchange diagram when a state transition attempt using an RRC connection procedure succeeds in a wireless communication system according to various embodiments of the present disclosure.
13B illustrates a signal exchange diagram when a state transition attempt using an RRC connection procedure is rejected by a distributed unit before delivery of a control message in a wireless communication system according to various embodiments of the present disclosure.
14 is a flowchart for rejecting state transition after delivery of a control message from a distribution unit of a base station in a wireless communication system according to various embodiments of the present disclosure.
15 illustrates a signal exchange diagram when an RRC state transition attempt is rejected by a distribution unit after transmission of a control message in a wireless communication system according to various embodiments of the present disclosure.
16 illustrates a signal exchange diagram for an RRC reconfiguration procedure in a wireless communication system according to various embodiments of the present disclosure.
17 illustrates another signal exchange diagram for an RRC reconfiguration procedure in a wireless communication system according to various embodiments of the present disclosure.
18 illustrates a signal exchange diagram for an RRC resumption procedure in a wireless communication system according to various embodiments of the present disclosure.
19 illustrates another signal exchange diagram for an RRC resumption procedure in a wireless communication system according to various embodiments of the present disclosure.
20 illustrates a signal exchange diagram for an initial access procedure in a wireless communication system according to various embodiments of the present disclosure.
21 illustrates another signal exchange diagram for an initial access procedure in a wireless communication system according to various embodiments of the present disclosure.

Terms used in the present disclosure are only used to describe a specific embodiment, and may not be intended to limit the scope of other embodiments. Singular expressions may include plural expressions unless the context clearly dictates otherwise. Terms used herein, including technical or scientific terms, may have the same meaning as commonly understood by one of ordinary skill in the art described in this disclosure. Among the terms used in the present disclosure, terms defined in general dictionaries may be interpreted as having the same or similar meanings as those in the context of the related art, and unless explicitly defined in the present disclosure, ideal or excessively formal meanings. not be interpreted as In some cases, even terms defined in the present disclosure cannot be interpreted to exclude embodiments of the present disclosure.

In various embodiments of the present disclosure described below, a hardware access method is described as an example. However, since various embodiments of the present disclosure include technology using both hardware and software, various embodiments of the present disclosure do not exclude software-based access methods.

Hereinafter, the present disclosure relates to an apparatus and method for managing a connection in a wireless communication system. Specifically, the present disclosure describes a technique for managing a connection in an environment in which a base station is divided into a central unit (CU) and a distributed unit (DU) in a wireless communication system.

In the following description, terms referring to signals, terms referring to channels, terms referring to control information, terms referring to network entities, terms referring to components of devices, messages and messages included in the message are used. Terms and the like that refer to information elements are illustrated for convenience of description. Accordingly, the present disclosure is not limited to the terms described below, and other terms having equivalent technical meanings may be used.

In addition, although the present disclosure describes various embodiments using terms used in some communication standards (eg, 3rd Generation Partnership Project (3GPP)), this is only an example for explanation. Various embodiments of the present disclosure may be easily modified and applied to other communication systems.

1 illustrates a wireless communication system according to various embodiments of the present disclosure. 1 illustrates a base station 110, a terminal 120, and a terminal 130 as some of nodes using a radio channel in a wireless communication system. Although FIG. 1 shows only one base station, other base stations identical to or similar to base station 110 may be further included.

Base station 110 is a network infrastructure that provides wireless access to terminals 120 and 130 . The base station 110 has coverage defined as a certain geographic area based on a distance over which a signal can be transmitted. The base station 110 includes 'access point (AP)', 'eNodeB (eNB)', '5G node (5th generation node)', 'wireless point', ' It may be referred to as a 'transmission/reception point (TRP)' or another term having an equivalent technical meaning.

Each of the terminal 120 and terminal 130 is a device used by a user and communicates with the base station 110 through a radio channel. In some cases, at least one of the terminal 120 and the terminal 130 may be operated without user involvement. That is, at least one of the terminal 120 and the terminal 130 is a device that performs machine type communication (MTC) and may not be carried by a user. Each of the terminal 120 and terminal 130 is a 'user equipment (UE)', 'mobile station', 'subscriber station', 'remote terminal', 'remote terminal' other than the terminal. It may be referred to as a 'wireless terminal', 'user device' or other terms having an equivalent technical meaning.

The base station 110, terminal 120, and terminal 130 may transmit and receive wireless signals in a mmWave band (eg, 28 GHz, 30 GHz, 38 GHz, and 60 GHz). At this time, in order to improve the channel gain, the base station 110, the terminal 120, and the terminal 130 may perform beamforming. Here, beamforming may include transmit beamforming and receive beamforming. That is, the base station 110, the terminal 120, and the terminal 130 may assign directivity to a transmitted signal or a received signal. To this end, the base station 110 and the terminals 120 and 130 may select serving beams 112, 113, 121 and 131 through a beam search or beam management procedure. After the serving beams 112, 113, 121, and 131 are selected, communication thereafter can be performed through a resource having a quasi co-located (QCL) relationship with the resource transmitting the serving beams 112, 113, 121, and 131.

If the large-scale characteristics of the channel carrying the symbol on the first antenna port can be inferred from the channel carrying the symbol on the second antenna port, the first antenna port and the second antenna port are said to be in a QCL relationship. can be evaluated. For example, a wide range of properties are delay spread, doppler spread, doppler shift, average gain, average delay, spatial receiver parameter may include at least one of them.

In the example described with reference to FIG. 1 , base station 110 has been described as a single device. However, base station 110 may be implemented to be divided into two or more devices. For example, a base station may include one central unit and at least one distribution unit. A structure of a base station divided into a central unit and a distribution unit may be referred to as a 'CU-DU split structure'. The central unit and the distribution unit may be distinguished in terms of protocol layers, and an example is shown in FIG. 2 below.

2 illustrates a protocol stack of a terminal and a base station in a wireless communication system according to various embodiments of the present disclosure. 2 illustrates a protocol structure for control, that is, a control plane. Referring to FIG. 2, the terminal 120 is radio frequency (RF), physical (PHY), media access control (MAC), radio link control (RLC), packet data convergence protocol (PDCP), radio resource control (RRC), etc. process the layers. The distribution unit 110-1 of the base station 110 processes layers such as RF, PHY, MAC, and RLC, and the central unit 110-2 of the base station 110 processes layers such as PDCH and RRC. Also, an interface between the distribution unit 110-1 and the central unit 110-2 may be referred to as 'F1'.

3 illustrates a configuration of a central unit of a base station in a wireless communication system according to various embodiments of the present disclosure. The configuration illustrated in FIG. 3 may be understood as a configuration of the distribution unit 110 - 1 of the base station 110 . '...' is used below. wealth', '… A term such as 'group' refers to a unit that processes at least one function or operation, and may be implemented as hardware, software, or a combination of hardware and software.

Referring to FIG. 3 , the distribution unit includes a wireless communication unit 310, a backhaul communication unit 320, a storage unit 330, and a control unit 340.

The wireless communication unit 310 performs functions for transmitting and receiving signals through a wireless channel. For example, the wireless communication unit 310 performs a conversion function between a baseband signal and a bit string according to the physical layer standard of the system. For example, during data transmission, the wireless communication unit 310 generates complex symbols by encoding and modulating a transmission bit stream. In addition, when receiving data, the wireless communication unit 310 restores the received bit stream by demodulating and decoding the baseband signal.

In addition, the wireless communication unit 310 up-converts the baseband signal into a radio frequency (RF) band signal, transmits the signal through an antenna, and down-converts the RF band signal received through the antenna into a baseband signal. To this end, the wireless communication unit 310 may include a transmit filter, a receive filter, an amplifier, a mixer, an oscillator, a digital to analog converter (DAC), an analog to digital converter (ADC), and the like. In addition, the wireless communication unit 310 may include a plurality of transmission and reception paths. Furthermore, the wireless communication unit 310 may include at least one antenna array composed of a plurality of antenna elements.

In terms of hardware, the wireless communication unit 310 may be composed of a digital unit and an analog unit, and the analog unit is composed of a plurality of sub-units according to operating power, operating frequency, etc. It can be. The digital unit may be implemented with at least one processor (eg, a digital signal processor (DSP)).

The wireless communication unit 310 transmits and receives signals as described above. Accordingly, all or part of the wireless communication unit 310 may be referred to as a 'transmitter', 'receiver', or 'transceiver'. Also, in the following description, transmission and reception performed through a radio channel are used to mean that the above-described processing is performed by the wireless communication unit 310 .

The backhaul communication unit 320 provides an interface for communicating with other nodes in the network. That is, the backhaul communication unit 320 converts a bit string transmitted from a distribution unit to another node, for example, a central unit, another connection node, another distribution unit, an upper node, a core network, etc., into a physical signal, and converts a bit string received from another node into a physical signal. Converts a physical signal into a bit string.

The storage unit 330 stores data such as basic programs, application programs, and setting information for operation of the distribution unit. The storage unit 330 may include volatile memory, non-volatile memory, or a combination of volatile and non-volatile memories. And, the storage unit 330 provides stored data according to the request of the control unit 340 .

The controller 340 controls overall operations of the distribution unit. For example, the control unit 340 transmits and receives signals through the wireless communication unit 310 or the backhaul communication unit 320 . Also, the control unit 340 writes data to and reads data from the storage unit 330 . In addition, the control unit 340 may perform protocol stack functions required by communication standards, that is, functions of PHY, MAC, and RLC layers. According to another implementation example, the protocol stack may be included in the wireless communication unit 310 . To this end, the controller 340 may include at least one processor.

According to various embodiments, the controller 340 may manage connections between terminals. For example, the control unit 340 may control an operation for determining whether to accept a procedure requested by a control message of an upper layer and informing the central unit of the determination result. According to an embodiment, the controller 340 receives a control message processed by the central unit from the terminal, receives a first control message processed by the central unit from the terminal, and rejects a procedure requested by the first control message. It is possible to transmit a modified first control message to the central unit to indicate that, and to receive a second control message indicating rejection of the procedure as a response to the modified first control message. According to another embodiment, the controller 340 receives a first control message processed by the central unit from the terminal, transmits the first control message to the central unit, and instructs the progress of the procedure as a response to the first control message. control to receive a second control message to drop the second control message in response to determining that the procedure requested by the first control message is rejected, and to transmit a third control message corresponding to the rejection of the procedure to the central unit. can do. For example, the controller 340 may control the distribution unit to perform operations according to various embodiments described later.

4 illustrates a configuration of a central unit of a base station in a wireless communication system according to various embodiments of the present disclosure. The configuration illustrated in FIG. 4 can be understood as a configuration of the central unit 110 - 2 of the base station 110 . '...' is used below. wealth', '… A term such as 'group' refers to a unit that processes at least one function or operation, and may be implemented as hardware, software, or a combination of hardware and software.

Referring to FIG. 4 , the central unit includes a backhaul communication unit 410, a storage unit 420, and a control unit 430.

The backhaul communication unit 410 provides an interface for communicating with other nodes in the network. That is, the backhaul communication unit 410 converts a bit string transmitted from the central unit to another node, for example, a distribution unit, another access node, another central unit, an upper node, a core network, etc., into a physical signal, and converts a bit string received from the other node into a physical signal. Converts a physical signal into a bit string. The backhaul communication unit 410 transmits and receives signals as described above. Accordingly, all or part of the backhaul communication unit 410 may be referred to as a 'transmitter', a 'receiver', or a 'transceiver'.

The storage unit 420 stores data such as basic programs for operation of the central unit, application programs, and setting information. The storage unit 420 may include volatile memory, non-volatile memory, or a combination of volatile and non-volatile memories. And, the storage unit 420 provides stored data according to the request of the control unit 430 .

The controller 430 controls overall operations of the central unit. For example, the control unit 430 transmits and receives signals through the backhaul communication unit 410 . Also, the control unit 430 writes data to and reads data from the storage unit 420 . In addition, the control unit 430 may perform protocol stack functions required by communication standards, that is, PDCP and RRC layer functions. To this end, the controller 430 may include at least one processor.

According to various embodiments, the controller 430 may manage connections between terminals. According to various embodiments, the controller 430 may manage a connection according to a control message received from a distribution unit. According to an embodiment, the control unit 430 receives the first control message generated by the terminal from the distribution unit and confirms that the first control message is modified to indicate that the procedure requested by the first control message is rejected. It may be controlled to transmit a second control message indicating rejection of the procedure. For example, the controller 430 may control the central unit to perform operations according to various embodiments described later.

5 illustrates a configuration of a terminal in a wireless communication system according to various embodiments of the present disclosure. The configuration illustrated in FIG. 5 may be understood as a configuration of the terminal 120 . '...' is used below. wealth', '… A term such as 'group' refers to a unit that processes at least one function or operation, and may be implemented as hardware, software, or a combination of hardware and software.

Referring to FIG. 5 , the terminal includes a communication unit 510, a storage unit 520, and a control unit 530.

The communication unit 510 performs functions for transmitting and receiving signals through a wireless channel. For example, the communication unit 510 performs a conversion function between a baseband signal and a bit string according to the physical layer standard of the system. For example, during data transmission, the communication unit 510 generates complex symbols by encoding and modulating a transmission bit stream. In addition, when receiving data, the communication unit 510 restores the received bit stream by demodulating and decoding the baseband signal. Also, the communication unit 510 up-converts the baseband signal into an RF band signal, transmits the signal through an antenna, and down-converts the RF band signal received through the antenna into a baseband signal. For example, the communication unit 510 may include a transmit filter, a receive filter, an amplifier, a mixer, an oscillator, a DAC, and an ADC.

Also, the communication unit 510 may include a plurality of transmission/reception paths. Furthermore, the communication unit 510 may include at least one antenna array composed of a plurality of antenna elements. In terms of hardware, the communication unit 510 may include a digital circuit and an analog circuit (eg, a radio frequency integrated circuit (RFIC)). Here, the digital circuit and the analog circuit may be implemented in one package. Also, the communication unit 510 may include multiple RF chains. Furthermore, the communication unit 510 may perform beamforming.

The communication unit 510 transmits and receives signals as described above. Accordingly, all or part of the communication unit 510 may be referred to as a 'transmitter', a 'receiver', or a 'transceiver'. Also, in the following description, transmission and reception performed through a radio channel are used to mean that the above-described processing is performed by the communication unit 510.

The storage unit 520 stores data such as basic programs for operation of the terminal, application programs, and setting information. The storage unit 520 may include volatile memory, non-volatile memory, or a combination of volatile and non-volatile memories. Also, the storage unit 520 provides stored data according to the request of the control unit 530 .

The controller 530 controls overall operations of the terminal. For example, the control unit 530 transmits and receives signals through the communication unit 510 . In addition, the controller 530 writes and reads data in the storage 520 . And, the control unit 530 may perform functions of the protocol stack required by the communication standards. To this end, the controller 530 may include at least one processor or microprocessor, or may be a part of the processor. Also, a part of the communication unit 510 and the control unit 530 may be referred to as a communication processor (CP).

6 illustrates a configuration of a communication unit in a wireless communication system according to various embodiments of the present disclosure. FIG. 6 illustrates an example of a detailed configuration of the wireless communication unit 310 of FIG. 3 or the communication unit 510 of FIG. 5 . Specifically, FIG. 6 is a part of the wireless communication unit 310 of FIG. 3 or the communication unit 510 of FIG. 5 and illustrates components for performing beamforming.

Referring to FIG. 6 , a wireless communication unit 210 or communication unit 310 includes an encoding and modulation unit 602, a digital beamforming unit 604, a plurality of transmission paths 606-1 to 606-N, and an analog beamforming unit 608.

The coding modulator 602 performs channel encoding. For channel encoding, at least one of a low density parity check (LDPC) code, a convolution code, and a polar code may be used. The encoding and modulation unit 602 generates modulation symbols by performing constellation mapping.

The digital beamformer 604 performs beamforming on digital signals (eg, modulation symbols). To this end, the digital beamformer 604 multiplies modulation symbols by beamforming weights. Here, beamforming weights are used to change the amplitude and phase of a signal, and may be referred to as a 'precoding matrix' or a 'precoder'. The digital beamformer 604 outputs digitally beamformed modulation symbols to a plurality of transmission paths 606-1 to 606-N. In this case, according to a multiple input multiple output (MIMO) transmission technique, modulation symbols may be multiplexed or the same modulation symbols may be provided to multiple transmission paths 606-1 to 606-N.

Multiple transmit paths 606-1 through 606-N convert digital beamformed digital signals to analog signals. To this end, each of the plurality of transmission paths 606-1 to 606-N may include an inverse fast fourier transform (IFFT) operator, a cyclic prefix (CP) inserter, a DAC, and an up-converter. The CP insertion unit is for an orthogonal frequency division multiplexing (OFDM) method, and may be excluded when another physical layer method (eg, filter bank multi-carrier (FBMC)) is applied. That is, the plurality of transmission paths 606-1 to 606-N provide independent signal processing processes for a plurality of streams generated through digital beamforming. However, depending on the implementation method, some of the components of the plurality of transmission paths 606-1 to 606-N may be used in common.

The analog beamformer 608 performs beamforming on an analog signal. To this end, the digital beamformer 604 multiplies analog signals by beamforming weights. Here, beamforming weights are used to change the magnitude and phase of a signal. Specifically, the analog beamformer 640 may be configured in various ways according to the connection structure between the plurality of transmission paths 630-1 to 630-N and antennas. For example, each of the plurality of transmission paths 630-1 to 630-N may be connected to one antenna array. As another example, multiple transmission paths 630-1 to 630-N may be connected to one antenna array. As another example, the plurality of transmission paths 630-1 to 630-N may be adaptively connected to one antenna array or to two or more antenna arrays.

In a system according to various embodiments, a terminal may operate in various states. For example, the terminal may operate in one of an RRC connected state, an RRC idle state, and an RRC inactive state. The RRC connection state may be referred to as an RRC 'active state' or an 'RRC normal state'. In the RRC connected state, all protocol layers of the UE are activated, and the UE can transmit/receive data. In the RRC idle state, the protocol layers of the terminal are inactivated, and resources on the core network are released. However, in the RRC idle state, the terminal may perform operations such as receiving broadcast information, updating a tracking area (TA), and receiving paging.

In the RRC inactive state, the protocol layers of the UE are inactive, but the connection between the UE and the core network is maintained. That is, in the case of an RRC inactive state, the connection with the core network is similar to the RRC connection state. In the RRC inactive state, apart from managing the idle state in the core network, the state of the terminal is separately managed in the radio access network (RAN), so that the terminal maintains an access stratum (AS) context and more quickly Allow transition to connected state. Due to the introduction of the RRC inactive state, various uses such as connectionless data transmission for small data in the inactive state as well as reduction in terminal power consumption can be implemented.

The UE may transition between the RRC connected state, the RRC idle state, and the RRC inactive state according to a given condition. For example, when transmission data occurs in a terminal operating in an RRC inactive state or an RRC idle state, the terminal may request state transition by transmitting a message for transitioning to an RRC connected state. Examples of procedures for state transition are described below with reference to FIGS. 7 and 8 .

7 illustrates a signal exchange diagram when context search is successful upon RRC state transition in a wireless communication system according to various embodiments of the present disclosure. 7 illustrates signal exchange between the terminal 120, the distribution unit 110-1 of the base station 110, and the central unit 110-2 of the base station 110.

Referring to FIG. 7 , in step 701, the terminal 120 operates in an RRC inactive state or an RRC idle state. Then, in step 703, the terminal 120 transmits an RRC connection resume request message. That is, when an event such as generation of data to be transmitted occurs, the terminal 120 transmits a message requesting a transition to the RRC connected state.

In step 705, the distribution unit 110-1 transmits an initial uplink RRC (RRC) message to the central unit 110-2. The initial uplink RRC message includes an RRC connection resume request message transmitted from the terminal 120. The RRC connection resume request message received by the distribution unit 110-1 is data including a MAC header and an RLC header. Therefore, with respect to the received data, the distribution unit 110-1 performs necessary processing in the MAC layer and the RLC layer, includes an RRC message (eg, RRC connection resumption request) to be transmitted to the central unit in the initial uplink RRC message, and then , can be delivered to the central unit 110-2. Additionally, the initial uplink RRC message may further include at least one of identification information of the terminal 120 (eg, cell-radio network temporary identity (C-RNTI)) and information about the resource allocation configuration of the distribution unit 110-1. . The initial uplink RRC message may be referred to as 'F1-application protocol (AP) initial uplink RRC message transfer message'.

In step 707, the central unit 110-2 retrieves the context of the terminal 120. Subsequently, in step 709, the central unit 110-2 transmits a UE context setup request message to the distributed unit 110-1. In step 711, the distribution unit 110-1 transmits a UE context setup response message.

Subsequently, in step 713, the central unit 110-2 transmits a downlink RRC message transfer message including an RRC connection resume message. In step 715, the distribution unit 110-1 transmits an RRC connection resume message. In step 717, the terminal 120 transmits an RRC connection resume complete message. In step 719, the distribution unit 110-1 transmits an uplink RRC message transfer message including an RRC connection resume complete message. Accordingly, in step 717, the terminal 120 transitions to the RRC connected state.

8 illustrates a signal exchange diagram when context search fails during RRC state transition in a wireless communication system according to various embodiments of the present disclosure. 8 illustrates signal exchange between the terminal 120, the distribution unit 110-1 of the base station 110, and the central unit 110-2 of the base station 110.

Referring to FIG. 8 , in step 801, the terminal 120 operates in an RRC inactive state or an RRC idle state. Then, in step 803, the terminal 120 transmits an RRC connection resume request message. That is, when an event such as generation of data to be transmitted occurs, the terminal 120 transmits a message requesting a transition to the RRC connected state. In step 805, the distribution unit 110-1 transmits an initial uplink RRC message to the central unit 110-2. The initial uplink RRC message includes an RRC connection resume request message transmitted from the terminal 120, and additionally, at least one of identification information (eg, C-RNTI) of the terminal 120 and information about the resource allocation configuration of the distribution unit 110-1. may further include.

In step 807, the central unit 110-2 fails to retrieve the context of the terminal 120. And, the central unit 110 - 2 determines that it can accommodate the terminal 120 . Accordingly, in step 809, the central unit 110-2 transmits a UE context setup message including an RRC connection setup message.

In step 811, the distribution unit 110-1 transmits an RRC connection establishment message. In step 813, the terminal 120 transmits an RRC connection establishment completion message. That is, after performing an operation necessary to establish an RRC connection, the terminal 120 transmits a message indicating that the RRC connection is established. Subsequently, in step 815, the distribution unit 110-1 transmits a UE context setup response message. For example, the UE context establishment response message may include an RRC connection establishment completion message. Accordingly, in step 717, the terminal 120 transitions to the RRC connected state.

Through the procedure of FIG. 7 or 8, the UE may transition from the RRC inactive state to the RRC connected state. However, acceptance of the request for state transition of the terminal is not always guaranteed. For example, if allocatable hardware resources, logical resources, physical resources, etc. are insufficient, the request for state transition may be rejected. A case in which a request for state transition is rejected will be described with reference to FIG. 9 .

9 illustrates a signal exchange diagram when an RRC state transition attempt is rejected in a wireless communication system according to various embodiments of the present disclosure. 9 illustrates signal exchange between the terminal 120, the distribution unit 110-1 of the base station 110, and the central unit 110-2 of the base station 110.

Referring to FIG. 9 , in step 901, the terminal 120 operates in an RRC inactive state or an RRC idle state. Then, in step 903, the terminal 120 transmits an RRC connection resume request message. That is, when an event such as generation of data to be transmitted occurs, the terminal 120 transmits a message requesting a transition to the RRC connected state. In step 905, the distribution unit 110-1 transmits an initial uplink RRC message to the central unit 110-2. The initial uplink RRC message includes an RRC connection resume request message transmitted from the terminal 120, and additionally, at least one of identification information (eg, C-RNTI) of the terminal 120 and information about the resource allocation configuration of the distribution unit 110-1. may further include.

In step 907, the central unit 110-2 determines to reject the request of the terminal 120. Requests can be denied for a variety of reasons. For example, the central unit 110 - 2 may reject the request of the terminal 120 according to lack of resources due to congestion. Accordingly, in step 909, the central unit 110-2 transmits a downlink RRC message transfer message. For example, the downlink RRC message transfer message may include an RRC message notifying rejection of RRC connection resumption. In step 911, the distributed unit 110-1 transmits an RRC connection reject message.

In the above example, the state transition request was rejected by the central unit. However, since the base station has a structure that is divided into a central unit and a distributed unit, failure of state transition may be determined by the distributed unit. In other words, the distribution unit may determine whether to accept the request of the terminal (eg, state transition request). These actions include 'connection control', 'resource allocation control', 'resource management', 'resource control', 'admission control', etc. can be referred to as

Since the central unit is a higher-order object than the distributed unit, when the central unit determines rejection, it can proceed with the procedure by notifying the determined rejection case. However, when the distribution unit determines rejection, it is impossible to process the state transition failure situation with only the existing message or information element (IE), or even if the failure situation is handled with the existing message, additional message exchange may be required. can Therefore, in order to avoid this inefficiency, a procedure capable of notifying a rejection situation from the distributed unit to the central unit is required.

In other words, unlike a conventional base station that is a single object, in the case of a base station structure composed of two objects, such as a central unit and a distributed unit, not only the central unit but also the distributed unit can determine connection rejection. Accordingly, the present disclosure proposes a method for notifying a central unit, which is an object separated from the distribution unit, of a connection rejection situation with respect to the distribution unit when the distribution unit determines connection rejection.

10 is a flowchart for rejecting a state transition prior to transmission of a control message of a distribution unit of a base station in a wireless communication system according to various embodiments of the present disclosure. 10 illustrates an operating method of the distribution unit 110-1.

Referring to FIG. 10 , in step 1001, the distribution unit receives data including a control message from the terminal. In this case, the distribution unit may receive lower layer data (eg, MAC packet data unit (PDU)) including a control message of an upper layer that is not processed by the distribution unit. In other words, the distributed units can receive control messages from higher layers that are processed by the central unit. Here, the control message may be an RRC layer message. Furthermore, the control message may be a message requesting state transition of the terminal. Specifically, the control message may be a message requesting a transition from an RRC inactive state to an RRC connected state.

In step 1003, the distribution unit determines whether the UE's request is acceptable. In other words, the distribution unit determines whether or not it can accommodate the procedure requested by the terminal (eg, state transition, connection establishment, etc.). For example, the distribution unit determines the terminal based on the available state of available hardware resources (eg, buffers, etc.), logical resources (eg, maximum number of users that can be accommodated, etc.), and physical resources (eg, time resources, frequency resources, etc.). of can be judged as acceptable. That is, regardless of the layer (eg, RRC layer) in which the control message is processed, the distribution unit may determine whether the terminal is acceptable based on the status of the layers managed by the distribution unit.

If it is determined that the UE's request cannot be accommodated, in step 1005, the distribution unit modifies the control message to indicate rejection of the UE's request. In other words, the distribution unit modifies the control message to indicate that it rejects the procedure requested by the control message. According to an embodiment, the distribution unit may insert a reject indication into the control message. For example, the distribution unit may insert a rejection indicator by adding, replacing, or removing at least one bit having a specific value at a specific location of the control message. As another example, the distributing unit may express the rejection indicator by removing a specific information element from the control message or replacing it with another value. That is, according to various embodiments, insertion of the rejection indicator may be understood as including substitution or deletion as well as addition of at least one bit.

At step 1007, the distribution unit forwards the control message to the central unit. To this end, the distribution unit may generate a transfer message including the modified control message and transmit the transfer message through an interface between the distribution unit and the central unit.

In the embodiment described with reference to FIG. 10 , the distribution unit determines whether the request of the terminal is acceptable. Various operations may be performed to determine whether the UE's request is acceptable. In other words, specific embodiments for determining whether the request of the terminal is acceptable may be defined in various ways. Specific embodiments for determining whether the request of the terminal is acceptable may be defined in various ways depending on what kind of information is based on and what kind of determination is performed.

According to an embodiment, in order to determine whether the request of the terminal is acceptable, the distribution unit may perform an operation performed after receiving the request for context setting from the central unit before receiving the request for context setting. can For example, before receiving a request for context setup, the distribution unit may attempt to reserve/allocate resources in the MAC/PHY layer for a signaling radio bearer (SRB) for transmitting control messages. Along with resource reservation/allocation of the MAC/PHY layer, determination of whether or not the UE's request can be accommodated may be performed. Specifically, the distribution unit may determine that the UE's request is acceptable if resource allocation for the signaling radio bearer succeeds, and may determine that the UE's request is not acceptable if resource allocation for the signaling radio bearer fails. If the resource reservation / allocation operation of the MAC / PHY layer is performed in advance, if the state transition succeeds as shown in FIG. 7 or 8, after a request for context setup is received (eg, after step 709 or after step 809), An operation for resource reservation/allocation of the MAC/PHY layer may be omitted.

Here, the signaling radio bearer considered in resource reservation/allocation of the MAC/PHY layer may include a signaling radio bearer (eg, SRB1) for a dedicated control channel (DCCH). In this case, the resource reservation/allocation of the MAC/PHY layer for transmitting the control message is based on parameters used by the UE when transmitting an RRC connection setup complete message through SRB1 (e.g., channel quality information (CQI)). ), SRS (sounding reference signal) reporting (reporting), etc.) may include MAC / PHY resource allocation operation for SRB1 for delivering to the central unit.

11 illustrates a flowchart of a central unit of a base station in a wireless communication system according to various embodiments of the present disclosure. 11 illustrates an operating method of the central unit 110-2.

Referring to FIG. 11 , in step 1101, the central unit receives a control message from the distribution unit. In other words, the central unit receives control messages generated by the terminals from the distributed units. Specifically, the central unit receives a transfer message including a control message, and confirms the control message in the transfer message. Here, the control message may be an RRC layer message. Furthermore, the control message may be a message requesting state transition of the terminal. For example, the control message may be a message requesting a transition from an RRC inactive state to an RRC connected state.

In step 1103, the central unit checks whether the control message indicates rejection of the UE's request. In other words, the central unit determines whether the control message indicates rejection by the distribution unit. According to an embodiment, the central unit may determine whether the control message indicates rejection by checking whether a rejection indicator is inserted into the control message. For example, the central unit may check whether at least one bit having a specific value has been added, replaced or removed in a specific location of the control message. As another example, the central unit may check whether a specific information element in the control message has been removed or replaced with a different value. That is, according to various embodiments, insertion of the rejection indicator may be understood as including substitution or deletion as well as addition of at least one bit.

If the control message indicates rejection of the UE's request, in step 1105, the central unit transmits a control message for rejection. That is, the central unit determines whether to reject connection setting of the terminal, ie, state transition, according to the determination of the distribution unit, and generates and transmits a control message for notifying the terminal of this. Specifically, the central unit may generate a control message notifying rejection, generate a transfer message including the control message, and then transmit the transfer message to the distribution unit.

If the control message does not indicate rejection of the request of the terminal, in step 1107, the central unit determines whether the request of the terminal can be accepted. The central unit may determine acceptance based on the status of the layers managed by the central unit. For example, the central unit may determine whether or not to accept based on whether or not the context of the terminal is stored, the resource state of corresponding layers, and the like. If the terminal's request cannot be accepted, the central unit proceeds to step 1105.

On the other hand, if the terminal's request can be accommodated, in step 1109, the central unit transmits a control message to proceed with a procedure according to the request. For example, when the terminal requests a state transition, the central unit may generate a control message indicating the state transition, generate a delivery message including the control message, and transmit the delivery message to the distribution unit. For example, the message indicating the state transition may include a message instructing to establish a context or a message instructing to establish an RRC connection.

According to the embodiments described with reference to FIGS. 10 and 11 , rejection of the request of the terminal determined by the distribution unit may be transmitted to the central unit. Accordingly, meaningless signaling for attempting unnecessary state transition may be reduced.

Also, as described above, the rejection indicator may be defined in various forms. The rejection indicator, which is an information element for the purpose of notifying the central unit of the rejection situation, is not limited to its name, and any parameter capable of notifying the central unit of the rejection situation in any form is sufficient. In addition, by intentionally omitting and transmitting the corresponding information element, an operation of notifying a rejection situation is also possible. For example, a delivery message including a rejection indicator (eg, an initial uplink RRC delivery message) may include at least one of the information elements shown in Table 1 below.

IE explanation DU UE ID Unique identifier for UE over the F1 interface within a DU PCI Physical Cell Identifier C-RNTI Cell-RNTI (Radio Network Temporary Identifier) RRC Container RRC message container which is delivered to CU Reject Indication Indicator that DU rejected allocating radio resource

10 and 11 describe the case where a control message for state transition is received, but a control message for another purpose may be received. Accordingly, according to another embodiment, the distribution node may further perform an operation of classifying the control message. That is, when the control message is received, the distributed node may determine whether the signaling requires resource allocation, such as a state transition, and perform the above-described operations if the signaling requires resource allocation. For example, a distributed node may classify a control message by examining a bit pattern of a specific location of the control message. According to another embodiment, the distribution node may perform an operation related to the rejection indicator for all control messages without message classification, and the central node may selectively use the rejection indicator.

Operations related to the aforementioned rejection indicators may be applied to various procedures. For example, if an RRC connection resumption request message is received and the RRC connection resumption rejection is determined by the distribution unit prior to transmitting the initial uplink RRC message transmission message, the above-mentioned rejection indicator indicates the RRC connection resumption by the distribution unit. Can be used to notify a denial to a central unit. By defining the reject indicator, when the distribution unit, which is a lower object, determines rejection, additional signaling for an operation to share information with the central unit, which is a higher object, is prevented, and procedure delay is minimized. An example in which the rejection indicator is used in the RRC connection resumption procedure will be described with reference to FIGS. 12A, 12B, 13A, and 13B.

12A illustrates a signal exchange diagram when a state transition attempt using an RRC resume procedure succeeds in a wireless communication system according to various embodiments of the present disclosure. 12A illustrates signal exchange between the terminal 120, the distribution unit 110-1 of the base station 110, and the central unit 110-2 of the base station 110.

Referring to FIG. 12A, in step 1201, the terminal 120 operates in an RRC inactive state or an RRC idle state. Then, in step 1203, the terminal 120 transmits an RRC connection resume request message. That is, when an event such as generation of data to be transmitted occurs, the terminal 120 transmits a message requesting a transition to the RRC connected state.

In step 1205, the distribution unit 110-1 determines acceptance of the state transition of the terminal 120. For example, the distribution unit 110-1 attempts resource allocation of a MAC/PHY layer for a signaling radio bearer for transmitting a control message, and determines the success of the resource allocation. In step 1207, the distribution unit 110-1 transmits an initial uplink RRC message including an RRC connection resumption request message to the central unit 110-2.

In step 1209, the central unit 110-2 retrieves the context of the terminal 120. 12A illustrates a case in which the context of the terminal 120 is stored in the central unit 110-2. Accordingly, the central unit 110 - 2 may acquire the context of the terminal 120 . That is, the central unit 110 - 2 may successfully retrieve the context of the UE 120 and determine to resume the data radio bearer (DRB).

Next, in step 1211, the central unit 110-2 transmits a UE context setup request message to the distributed unit 110-1. Specifically, as the context of the terminal 120 is obtained, the central unit 110 - 2 may allocate a UE F1-AP information element (IE) for the terminal 120 and transmit a message requesting context setting. When context setting is requested from the central unit 110-2, the distribution unit 110-1 sets the context of the terminal 120. And, in step 1213, the distribution unit 110-1 transmits a UE context setup response message.

Subsequently, in step 1215, the central unit 110-2 transmits a downlink RRC message transfer message including an RRC connection resume message. In step 1217, the distribution unit 110-1 transmits an RRC connection resume message. Thereafter, operations for the terminal 120 to transition to the RRC connected state are performed. For example, although not shown in FIG. 12A, the terminal 120 transmits an RRC connection resume complete message to the distribution unit 110-1, and the distribution unit 110-1 transmits the RRC connection resume complete message to the uplink. A link RRC message transfer message may be transmitted to the central unit 110-2. Accordingly, the terminal 120 may transition to an RRC connected state.

12B illustrates a signal exchange diagram when a state transition attempt using an RRC resume procedure is rejected by a distributed unit before delivery of a control message in a wireless communication system according to various embodiments of the present disclosure. 12A illustrates signal exchange between the terminal 120, the distribution unit 110-1 of the base station 110, and the central unit 110-2 of the base station 110.

Referring to FIG. 12B, in step 1251, the terminal 120 operates in an RRC inactive state or an RRC idle state. Then, in step 1253, the terminal 120 transmits an RRC connection resume request message. That is, when an event such as generation of data to be transmitted occurs, the terminal 120 transmits a message requesting a transition to the RRC connected state.

In step 1255, the distribution unit 110-1 determines rejection of the state transition of the terminal 120. For example, the distribution unit 110-1 attempts resource allocation of a MAC/PHY layer for a signaling radio bearer for transmitting a control message, and determines resource allocation failure. In step 1257, the distribution unit 110-1 transmits an initial uplink RRC message including a rejection indicator to the central unit 110-2. That is, if the distribution unit 110-1 determines RRC connection resumption refusal before transmitting the initial uplink RRC message, the distribution unit 110-1 sends the initial uplink RRC message to the central unit 110-2 for the purpose of notifying the rejection situation. Include reject directives.

In step 1259, the central unit 110-2 omits the search operation for the context of the terminal 120. That is, upon checking the rejection indicator, the central unit 110 - 2 determines that the terminal 120 rejects the state transition request without further determination. Accordingly, in step 1261, the central unit 110-2 transmits a final downlink RRC message transfer message including an RRC connection reject message. That is, the central unit 110-2, having received the initial uplink RRC message including the reject indicator, does not perform a new context assignment operation, and immediately transmits an RRC connection resume reject message or a downlink RRC message delivery message including the RRC connection reject message. is transmitted to the distribution unit 110-1.

In step 1263, the distribution unit 110-1 transmits an RRC connection reject message to the terminal 120. Upon receiving the downlink RRC message delivery message including the RRC connection resume rejection message or the RRC connection rejection message, the distribution unit 110 - 1 forwards the RRC message to the terminal 120 . Accordingly, the terminal 120 is finally notified of the failure of the state transition operation to the RRC connected state.

13A illustrates a signal exchange diagram when a state transition attempt using an RRC connection procedure succeeds in a wireless communication system according to various embodiments of the present disclosure. 13A illustrates signal exchange between the terminal 130, the distribution unit 110-1 of the base station 110, and the central unit 110-2 of the base station 110.

Referring to FIG. 13A, in step 1301, the terminal 130 operates in an RRC inactive state or an RRC idle state. Then, in step 1303, the terminal 130 transmits an RRC connection request message. That is, when an event such as generation of data to be transmitted occurs, the terminal 130 transmits a message requesting a transition to the RRC connected state.

In step 1305, the distribution unit 110-1 determines acceptance of the state transition of the terminal 130. For example, the distribution unit 110-1 attempts resource allocation of a MAC/PHY layer for a signaling radio bearer for transmitting a control message, and determines the success of the resource allocation. In step 1307, the distribution unit 110-1 transmits an initial uplink RRC message including an RRC connection request message to the central unit 110-2.

In step 1309, the central unit 110-2 retrieves the context of the terminal 130. 13A illustrates a case in which the context of the terminal 130 is stored in the central unit 110-2. Accordingly, the central unit 110 - 2 may acquire the context of the terminal 130 . That is, the central unit 110 - 2 may successfully retrieve the context of the UE 130 and determine to connect a data radio bearer (DRB).

Subsequently, in step 1311, the central unit 110-2 transmits a UE context setup request message to the distributed unit 110-1. Specifically, as the context of the terminal 130 is obtained, the central unit 110 - 2 may allocate a UE F1-AP information element for the terminal 130 and transmit a message requesting context setup. When context setting is requested from the central unit 110 - 2 , the distribution unit 110 - 1 sets the context of the terminal 130 . And, in step 1313, the distribution unit 110-1 transmits a UE context setup response message.

Subsequently, in step 1315, the central unit 110-2 transmits a downlink RRC message delivery message including an RRC connection setup message. In step 1317, the distribution unit 110-1 transmits an RRC connection message. Thereafter, operations for the terminal 130 to transition to the RRC connected state are performed. For example, although not shown in FIG. 13A, the terminal 130 transmits an RRC connection setup complete message to the distributed unit 110-1, and the distributed unit 110-1 transmits an uplink link including the RRC connection complete message. An RRC message transfer message may be transmitted to the central unit 110-2. Accordingly, the terminal 130 may transition to an RRC connected state.

13B illustrates a signal exchange diagram when a state transition attempt using an RRC connection procedure is rejected by a distributed unit before delivery of a control message in a wireless communication system according to various embodiments of the present disclosure. 13A illustrates signal exchange between the terminal 130, the distribution unit 110-1 of the base station 110, and the central unit 110-2 of the base station 110.

Referring to FIG. 13B, in step 1351, the terminal 120 operates in an RRC inactive state or an RRC idle state. Then, in step 1353, the terminal 120 transmits an RRC connection request message. That is, when an event such as generation of data to be transmitted occurs, the terminal 120 transmits a message requesting a transition to the RRC connected state.

In step 1355, the distribution unit 110-1 determines rejection of the state transition of the terminal 120. For example, the distribution unit 110-1 attempts resource allocation of a MAC/PHY layer for a signaling radio bearer for transmitting a control message, and determines resource allocation failure. In step 1357, the distribution unit 110-1 transmits an initial uplink RRC message including a rejection indicator to the central unit 110-2. That is, when the distribution unit 110-1 determines RRC connection rejection before transmitting the initial uplink RRC message, the distribution unit 110-1 rejects the initial uplink RRC message for the purpose of notifying the central unit 110-2 of the rejection situation. Include directives.

In step 1359, the central unit 110-2 omits the search operation for the context of the terminal 120. That is, upon checking the rejection indicator, the central unit 110 - 2 determines that the terminal 120 rejects the state transition request without further decision. Accordingly, in step 1361, the central unit 110-2 transmits a final downlink RRC message transfer message including an RRC connection reject message. That is, the central unit 110-2, having received the initial uplink RRC message including the rejection indicator, does not perform a new context assignment operation and immediately transmits a downlink RRC message delivery message including an RRC connection rejection message to the distribution unit 110-1. send to

In step 1363, the distribution unit 110-1 transmits an RRC connection reject message to the terminal 120. Upon receiving the downlink RRC message transfer message including the RRC connection reject message, the distribution unit 110 - 1 forwards the RRC message to the terminal 120 . Accordingly, the terminal 120 is finally notified of the failure of the state transition operation to the RRC connected state.

As described above, the rejection state determined by the distribution unit may be transmitted to the central unit using the rejection indicator. However, before the initial uplink RRC message transfer message is transmitted, whether or not the UE can accept may not be determined. That is, after the initial uplink RRC message transfer message is transmitted, the rejection state may be determined by the distribution unit. In this case, since the rejection indicator is not included, if the terminal is not rejected by the central unit, the state transition procedure will proceed. In addition, when it is determined that the terminal accepts rejection before the initial uplink RRC message transfer message is transmitted, but the rejection indicator is missing, the same case may occur. If the state transition procedure proceeds due to delay in determining the rejection situation or omission of the rejection indicator, this means inefficiency due to unnecessary signaling. Accordingly, the present disclosure proposes a method for preparing for a case where a rejection indicator is not transmitted.

14 is a flowchart for rejecting state transition after delivery of a control message from a distribution unit of a base station in a wireless communication system according to various embodiments of the present disclosure. 14 illustrates an operating method of the distribution unit 110-1.

Referring to FIG. 14 , in step 1401, the distribution unit receives data including a control message from the terminal. Here, the control message may be an RRC layer message. Furthermore, the control message may be a message requesting state transition of the terminal. For example, the control message may be a message requesting a transition from an RRC inactive state to an RRC connected state.

At step 1403, the distribution unit forwards the control message to the central unit. To this end, the distribution unit may generate a delivery message including a control message and transmit the delivery message through an interface between the distribution unit and the central unit.

In step 1405, the distribution unit receives a control message for processing from the central unit. If the procedure requested by the terminal is a state transition, the request for the state transition of the terminal is accepted by the central unit, and accordingly, the distribution unit can receive a downlink RRC message transfer message including a control message for the state transition. can For example, the control message may include a context establishment request message or an RRC connection establishment message.

In step 1407, the distribution unit determines whether the UE's request is acceptable. For example, the distribution unit determines the terminal based on the available state of available hardware resources (eg, buffers, etc.), logical resources (eg, maximum number of users that can be accommodated, etc.), and physical resources (eg, time resources, frequency resources, etc.). of can be judged as acceptable. That is, irrespective of the layer (eg, RRC layer) in which the control message is processed, the distribution unit may determine whether to accept the request based on the status of the layers managed by the distribution unit. The operation of step 1407 may be understood as an operation of confirming the decision before performing step 1403 or an operation of making a new decision.

If it is determined that the request of the terminal cannot be accommodated, in step 1409, the distribution unit transmits a control message for stopping the procedure to the central unit. That is, the distribution unit generates and transmits a control message corresponding to rejection without transferring the control message to the terminal. Accordingly, a procedure (eg, state transition) requested by the terminal may be stopped.

If it is determined that the request of the terminal can be accommodated, in step 1411, the distribution unit transmits a control message for proceeding with the terminal to the terminal. That is, the distribution unit may transmit a control message to the terminal so that a procedure for state transition proceeds.

As in the embodiment described with reference to FIG. 14 , even if the rejection indicator is not used, unnecessary procedures can be prevented. In other words, even if the rejection indicator is omitted as shown in FIG. 14, the procedure may be terminated promptly according to the DU's decision. Here, the omission of the refusal indicator means that an error occurs in modifying the message even though acceptance refusal is determined, or it takes a long time to determine acceptance (e.g., a time limit for transmitting a control message), or This can happen for a variety of reasons, including a change in circumstances. An example in which the procedure of FIG. 14 is applied to an RRC connection resumption procedure will be described with reference to FIG. 15 below.

15 illustrates a signal exchange diagram when an RRC state transition attempt is rejected by a distribution unit after transmission of a control message in a wireless communication system according to various embodiments of the present disclosure. 15 illustrates signal exchange between the terminal 120, the distribution unit 110-1 of the base station 110, and the central unit 110-2 of the base station 110.

Referring to FIG. 15 , in step 1501, the terminal 120 operates in an RRC inactive state or an RRC idle state. Then, in step 1503, the terminal 120 transmits an RRC connection resume request message. That is, when an event such as generation of data to be transmitted occurs, the terminal 120 transmits a message requesting a transition to the RRC connected state.

In step 1503, the terminal 120 transmits an RRC connection resume request message. That is, when an event such as generation of data to be transmitted occurs, the terminal 120 transmits a message requesting a transition to the RRC connected state.

In step 1505, the distribution unit 110-1 transmits an initial uplink RRC message transfer message to the central unit 110-2. The initial uplink RRC message transfer message includes an RRC connection resume request message transmitted from the terminal 120. Additionally, the initial uplink RRC message may further include at least one of identification information (eg, C-RNTI) of the terminal 120 and information about resource allocation configuration of the distribution unit 110-1.

In step 1507, the central unit 110-2 retrieves the context of the terminal 120. 15 illustrates a case in which the context of the terminal 120 is stored in the central unit 110-2. Accordingly, the central unit 110 - 2 may acquire the context of the terminal 120 . That is, the central unit 110 - 2 may successfully retrieve the context of the UE 120 and determine to resume the data radio bearer.

In step 1509, the central unit 110-2 transmits a UE context establishment request message including RRC connection resumption to the distributed unit 110-1. Specifically, as the context of the terminal 120 is acquired, the central unit 110 - 2 may allocate a UE F1-AP information element for the terminal 120 and transmit a message requesting context setup.

In step 1511, the distribution unit 110-1 determines rejection of the terminal 120 and drops an RRC connection resume message. For example, this step may be a situation in which the distribution unit 110-1 determines rejection before step 1505 but the insertion of the rejection indicator is omitted, or a situation in which it determines rejection for the terminal 120 after step 1505. In other words, the reporting step is when the distribution unit 110-1 determines rejection of RRC connection resumption after transmission of the initial uplink RRC message transfer message or before transmission of the initial uplink RRC message transfer message in the distribution unit 110-1. It may be a case in which rejection is determined, but an operation of adding a rejection indicator to the initial uplink RRC message transfer message is omitted. Accordingly, the distribution unit 110-1 does not transfer the RRC connection resume message to the terminal 120, but drops it.

In step 1513, the distribution unit 110-1 transmits a UE context setup reject message. For example, the distribution unit 110-1 may generate a UE context setup reject message and transmit an uplink RRC message transfer message including the UE context setup reject message. If rejection is determined after transmission or before initial uplink RRC message transmission, but the rejection indicator is missing, the distribution unit 110-1 configures the UE context even if the downlink RRC delivery message including the RRC connection resume message is received. By promoting the rejection message to the central unit 110-2, it is possible to perform a rejection operation by the distribution unit 110-1 for the RRC connection resumption request.

In step 1515, the central unit 110-2 removes the context of the terminal 120. That is, the central unit 110 - 2 ends the state transition procedure of the terminal 120 . Then, in step 1517, the state transition procedure of the terminal 120 may be performed again.

As in the above-described various embodiments, in the state transition procedure, the procedure may be quickly terminated by rejecting the distributed unit. Although the above-described embodiments exemplify an RRC connection resumption procedure, the above-described embodiments may also be applied to an initial access procedure and an RRC reestablishment procedure. Examples related to the RRC resetting procedure with reference to FIGS. 16 and 17, examples related to the RRC resume procedure with reference to FIGS. 18 and 19, and examples related to the initial access procedure with reference to FIGS. 20 and 21 hereinafter Examples are described.

16 illustrates a signal exchange diagram for an RRC reconfiguration procedure in a wireless communication system according to various embodiments of the present disclosure.

Referring to FIG. 16 , in step 1601, the terminal 120 transmits an RRC connection reestablishment request message to transition to an RRC connected state. In step 1603, the distribution unit 110-1 allocates resources. Here, the resource may include a signaling radio bearer. In step 1605, the distribution unit 110-1 transmits an initial uplink RRC message. That is, the distribution unit 110-1 includes and transmits a corresponding RRC message (eg, an RRC connection reconfiguration request message) in an F1-AP initial uplink RRC message transfer message related to a non-UE. Additionally, the initial uplink RRC message transfer message may include the C-RNTI of the terminal 120, and may further include at least one of resource allocation configuration information (eg, radio Resource Config Dedicated) and a rejection indicator. Thereafter, the procedure branches to a first success case 1610 , a second success case 1630 , a first failure case 1650 , and a second failure case 1670 .

According to the first success situation 1610, in step 1611, the central unit 110-2 successfully retrieves the UE context stored in the distributed unit 110-1 and the central unit 110-2. Accordingly, the central unit 110 - 2 may allocate a CU UE F1AP ID (identifier) for the terminal 120 . Subsequently, in step 1613, the central unit 110-2 transmits a downlink RRC message delivery message including an RRC connection reestablishment message. That is, the RRC connection reconfiguration message is encapsulated in a downlink RRC message transfer message. Additionally, the downlink RRC message transfer message may further include information for retrieving a UE context (eg, previous CU UE F1AP ID, previous DU UE F1AP ID). In step 1615, the distribution unit 110-1 searches for a UE context according to the information received in step 1613, and transmits an RRC connection reconfiguration message. In step 1617, the terminal 120 transmits an RRC connection reestablishment complete message to the distributed unit 110-1. In step 1619, the distribution unit 110-1 encapsulates an RRC message, that is, an RRC connection reconfiguration complete message into an F1-AP uplink RRC message delivery message, and transmits the uplink RRC message delivery message to the central unit 110-2.

According to the second success situation 1630, in step 1631, the central unit 110-2 successfully retrieves the UE context stored in the central unit 110-2. That is, the second success situation 1630 is an example corresponding to the case where the UE context is not stored in the distribution unit 110-1. In step 1633, the central unit 110-2 transmits a UE context setup request message including data radio bearer related information. In step 1635, the distribution unit 110-1 transmits a UE context setup response message. In step 1637, the central unit 110-2 transmits a downlink RRC message delivery message including an RRC connection reconfiguration message. In step 1639, the distribution unit 110-1 transmits an RRC connection reconfiguration message. In step 1641, the terminal 120 transmits an RRC connection reconfiguration complete message. In step 1643, the distribution unit 110-1 encapsulates an RRC message, that is, an RRC connection reconfiguration complete message into an F1-AP uplink RRC message delivery message, and transmits the uplink RRC message delivery message to the central unit 110-2.

According to the first failure condition 1650, in step 1651, since the UE context is not stored in the central unit 110-2, the central unit 110-2 fails to retrieve the UE context. In step 1653, the central unit 110-2 transmits a downlink RRC message delivery message including an RRC connection reestablishment reject message. In step 1655, the distribution unit 110-1 transmits an RRC connection reconfiguration reject message to the terminal 120.

According to the second failure situation 1670, in step 1671, since the distribution unit 110-1 determines that even one non-guaranteed bit rate (GBR) data radio bearer cannot be accepted, the central unit 110-2 performs a state transition. decide to reject That is, the second failure condition 1670 is an example corresponding to a case in which the rejection indicator is included in the initial uplink RRC message transfer message transmitted in step 1605 . That is, the second failure situation 1670 is a case where the distribution unit 110-1 determines that the RRC connection is rejected before transmitting the initial uplink RRC message transfer message, and the distribution unit 110-1 determines that the initial uplink RRC is rejected. Include a reject indicator in the message forwarding message. In step 1673, the central unit 110-2 transmits a downlink RRC message transfer message including an RRC connection reconfiguration reject message. In other words, the central unit 110-2, having received the initial uplink RRC message transfer message including the reject indicator, does not perform a new UE context assignment operation and immediately transmits a downlink RRC message transfer message including an RRC connection reject message. do. In step 1675, the distribution unit 110-1 transmits an RRC connection reconfiguration reject message to the terminal 120. That is, the distribution unit 110-1 receiving the downlink RRC message transfer message including the RRC connection reject message forwards the corresponding RRC message to the terminal 120, so that the terminal 120 is finally notified of the failure of transition to the RRC connected state. do.

17 illustrates another signal exchange diagram for an RRC reconfiguration procedure in a wireless communication system according to various embodiments of the present disclosure.

Referring to FIG. 17 , in step 1601, the terminal 120 transmits an RRC connection reestablishment request message to transition to an RRC connected state. In step 1603, the distribution unit 110-1 transmits an initial uplink RRC message. That is, the distribution unit 110-1 includes and transmits a corresponding RRC message (eg, an RRC connection reconfiguration request message) in an F1-AP initial uplink RRC message transfer message related to a non-UE. Thereafter, the procedure branches to a first success condition 1610, a second success condition 1630, a first failure condition 1650, and a second failure condition 1670.

According to the first success situation 1610, in step 1611, the central unit 110-2 successfully retrieves the UE context stored in the distributed unit 110-1 and the central unit 110-2. Next, in step 1613, the central unit 110-2 transmits a UE context setup request message including information for retrieving a UE context. In step 1615, the distribution unit 110-1 transmits a UE context setup response message. In step 1617, the central unit 110-2 transmits a downlink RRC message delivery message including an RRC connection reconfiguration message. In step 1619, the distributed unit 110-1 transmits an RRC connection reconfiguration message. In step 1621, the terminal 120 transmits an RRC connection reconfiguration complete message. In step 1623, the distribution unit 110-1 encapsulates an RRC message, that is, an RRC connection reconfiguration complete message into an F1-AP uplink RRC message delivery message, and transmits the uplink RRC message delivery message to the central unit 110-2.

According to the second success situation 1630, in step 1631, the central unit 110-2 successfully retrieves the UE context stored in the central unit 110-2. Subsequently, in step 1633, the central unit 110-2 transmits a UE context establishment request message including data radio bearer related information. In step 1635, the distribution unit 110-1 transmits a UE context setup response message. In step 1637, the central unit 110-2 transmits a downlink RRC message delivery message including an RRC connection reconfiguration message. In step 1639, the distribution unit 110-1 transmits an RRC connection reconfiguration message. In step 1641, the terminal 120 transmits an RRC connection reconfiguration complete message. In step 1643, the distribution unit 110-1 encapsulates an RRC message, that is, an RRC connection reconfiguration complete message into an F1-AP uplink RRC message delivery message, and transmits the uplink RRC message delivery message to the central unit 110-2.

According to the first failure condition 1650, in step 1651, since the UE context is not stored in the central unit 110-2, the central unit 110-2 fails to retrieve the UE context. In step 1653, the central unit 110-2 transmits a downlink RRC message delivery message including an RRC connection reestablishment reject message. In step 1655, the distribution unit 110-1 transmits an RRC connection reconfiguration reject message to the terminal 120.

According to the second failure situation 1670, in step 1671, the central unit 110-2 successfully retrieves the UE context stored in the central unit 110-2. Subsequently, in step 1673, the central unit 110-2 transmits a UE context establishment request message including data radio bearer related information. At this time, the distribution unit 110-1 determines that the terminal 120 cannot be accommodated, and in step 1675, transmits a UE context setup failure message. In step 1677, the central unit 110-2 transmits a downlink RRC message transfer message including an RRC connection reconfiguration reject message. In step 1679, the distribution unit 110-1 transmits an RRC connection reconfiguration reject message to the terminal 120.

The procedures of FIGS. 16 and 17 are all related to RRC connection re-establishment. The procedure of FIG. 16 has a technical advantage of reducing the latency of connection re-establishment in some situations, and the procedure of FIG. 17 adds information on resource allocation configuration (eg, radio Resource Config Dedicated) and a rejection indicator. It has the technical advantage of no motion.

18 illustrates a signal exchange diagram for an RRC resumption procedure in a wireless communication system according to various embodiments of the present disclosure.

Referring to FIG. 18 , in step 1801, the terminal 120 transmits an RRC connection resume request message to transition to the RRC connected state. In step 1803, the distribution unit 110-1 allocates resources. Here, the resource may include a signaling radio bearer (SRB). In step 1805, the distribution unit 110-1 transmits an initial uplink RRC message. That is, the distribution unit 110-1 includes and transmits a corresponding RRC message (eg, an RRC connection resumption request message) in an F1-AP initial uplink RRC message transfer message related to a non-UE. Additionally, the initial uplink RRC message transfer message may include the C-RNTI of the terminal 120, and may further include at least one of resource allocation configuration information (eg, radio Resource Config Dedicated) and a rejection indicator. Thereafter, the procedure branches to a success situation 1810, a successful fallback situation 1830, and a failure situation 1850.

According to the first success situation 1810, in step 1811, the central unit 110-2 successfully retrieves the UE contexts stored in the distributed unit 110-1 and the central unit 110-2, and determines to resume at least one data radio bearer. do. Accordingly, the central unit 110 - 2 may allocate a CU UE F1AP ID for the terminal 120 . In step 1813, the central unit 110-2 transmits a UE context setup request message. In step 1815, the distribution unit 110-1 transmits a UE context setup response message including resource allocation information (eg, radio Resource Config Dedicated) for at least one data radio bearer. In step 1817, the central unit 110-2 transmits a downlink RRC message transfer message including an RRC connection resume message. In step 1819, the distribution unit 110-1 transmits an RRC connection resume message. In step 1821, the terminal 120 transmits an RRC connection resume complete message. In step 1823, the distribution unit 110-1 transmits an RRC message, that is, an uplink RRC message transfer message including an RRC connection reconfiguration complete message to the central unit 110-2.

According to the successful fallback situation 1830, in step 1831, the central unit 110-2 fails to search for the UE context and determines to accept the access request. Accordingly, the central unit 110 - 2 may allocate a CU UE F1AP ID for the terminal 120 . Subsequently, in step 1833, the central unit 110-2 generates an RRC connection setup message, encapsulates the RRC connection setup message in a downlink RRC message transfer message, and transmits the message. In step 1835, the distributed unit 110-1 transmits an RRC connection setup message. In step 1837, the terminal 120 transmits an RRC connection setup complete message. In step 1839, the distribution unit 110-1 encapsulates the corresponding RRC message into an F1-AP UL RRC message transfer message and transmits the F1-AP UL RRC message transfer message.

According to the failure situation 1850, in step 1851, the central unit 110-2 skips the context search because the distribution unit 110-1 includes the reject indicator. A second failure condition 1850 is an example corresponding to a case in which a reject indicator is included in the initial uplink RRC message transfer message transmitted in step 1805 . That is, the second failure situation 1870 is a case where the distribution unit 110-1 determines that the RRC connection is rejected before transmitting the initial uplink RRC message transfer message, and the distribution unit 110-1 determines that the initial uplink RRC is rejected. Include a reject indicator in the message forwarding message. In step 1873, the central unit 110-2 transmits a downlink RRC message transfer message including an RRC connection reconfiguration reject message. In other words, the central unit 110-2, having received the initial uplink RRC message transfer message including the reject indicator, does not perform a new UE context assignment operation and immediately transmits a downlink RRC message transfer message including an RRC connection reject message. do. In step 1875, the distribution unit 110-1 transmits an RRC connection reconfiguration reject message to the terminal 120. That is, the distribution unit 110-1 receiving the downlink RRC message transfer message including the RRC connection reject message forwards the corresponding RRC message to the terminal 120, so that the terminal 120 is finally notified of the failure of transition to the RRC connected state. do.

19 illustrates another signal exchange diagram for an RRC resumption procedure in a wireless communication system according to various embodiments of the present disclosure.

Referring to FIG. 19 , in step 1801, the terminal 120 transmits an RRC connection resume request message to transition to the RRC connected state. In step 1803, the distribution unit 110-1 transmits an initial uplink RRC message. That is, the distribution unit 110-1 includes and transmits a corresponding RRC message (eg, an RRC connection resumption request message) in an F1-AP initial uplink RRC message transfer message related to a non-UE. Thereafter, the procedure branches to a success situation 1810 and a failure situation 1830 .

According to the success situation 1810, in step 1811, the central unit 110-2 successfully retrieves the UE contexts stored in the distributed unit 110-1 and the central unit 110-2, and determines to resume at least one data radio bearer. Alternatively, the central unit 110-2 fails to search the UE context and determines to accept the access request. Accordingly, in step 1813, the central unit 110-2 transmits a UE context setup request message including a cause value. In step 1815, the distribution unit 110-1 allocates resources. Here, the resource may include a signaling radio bearer (SRB). In step 1817, the distribution unit 110-1 transmits a UE context setup response message including resource allocation information (eg, radio Resource Config Dedicated) for at least one data radio bearer. In step 1819, the central unit 110-2 transmits a downlink RRC message transfer message including an RRC connection resume message or an RRC connection setup message. For example, if the context search succeeds in step 1811, an RRC connection resume message may be included, whereas if the context search fails, an RRC connection setup message may be included. In step 1821, the distribution unit 110-1 transmits an RRC connection resume message or an RRC connection establishment message. In step 1823, the terminal 120 transmits an RRC connection resume complete message or an RRC connection setup complete message. In step 1825, the distribution unit 110-1 transmits an RRC message, that is, an uplink RRC message delivery message including an RRC connection resetting complete message or an RRC connection establishment complete message to the central unit 110-2.

According to the failure situation 1830 , in step 1831 , the central unit 110 - 2 determines whether the UE context search is successful or the access is accepted. Accordingly, in step 1833, the central unit 110-2 transmits a UE context setup request message including a cause value. In step 1835, the distribution unit 110-1 fails to allocate resources. That is, the distribution unit 110-1 determines that the terminal 120 cannot be accommodated. In step 1837, the distribution unit 110-1 transmits a UE context setup failure message. In step 1839, the central unit 110-2 transmits a downlink RRC message transfer message including an RRC connection reject message. In step 1841, the distribution unit 110-1 transmits an RRC connection reject message to the terminal 120.

The procedures of FIGS. 18 and 19 are all related to RRC connection resumption. The procedure of FIG. 18 has a technical advantage of enabling flexible implementation and reducing latency for resuming. The procedure of Figure 19 has the technical advantage of providing a unified procedure for success situations.

20 illustrates a signal exchange diagram for an initial access procedure in a wireless communication system according to various embodiments of the present disclosure.

Referring to FIG. 20 , in step 2001, the UE 120 transmits an RRC connection request message to transition to an RRC connected state. In step 2003, the distribution unit 110-1 allocates resources. Here, the resource may include a signaling radio bearer (SRB). In step 2005, the distribution unit 110-1 transmits an initial uplink RRC message. That is, the distribution unit 110-1 includes and transmits a corresponding RRC message (eg, an RRC connection request message) in an F1-AP initial uplink RRC message transfer message related to a non-UE. Additionally, the initial uplink RRC message transfer message may include the C-RNTI of the terminal 120, and may further include at least one of resource allocation configuration information (eg, radio Resource Config Dedicated) and a rejection indicator. Thereafter, the procedure branches to a success situation 2010 and a failure situation 2030.

According to success situation 2010, in step 2011, the central unit 110-2 transmits a downlink RRC message transfer message including an RRC connection setup message. In step 2013, the distribution unit 110-1 transmits an RRC connection establishment message. In step 2015, the terminal 120 transmits an RRC connection setup complete message. In step 2017, the distribution unit 110-1 transmits an uplink RRC message delivery message including an RRC connection setup completion message.

According to failure situation 2030, in step 2031, the central unit 110-2 transmits a downlink RRC message delivery message including an RRC connection reject message. In step 2033, the distribution unit 110-1 transmits an RRC connection reject message to the terminal 120. That is, the terminal 120 is finally notified of the failure of the transition operation to the RRC connected state.

21 illustrates another signal exchange diagram for an initial access procedure in a wireless communication system according to various embodiments of the present disclosure.

Referring to FIG. 21 , in step 2101, the terminal 120 transmits an RRC connection request message to transition to an RRC connected state. In step 2103, the distribution unit 110-1 transmits an initial uplink RRC message. That is, the distribution unit 110-1 includes and transmits a corresponding RRC message (eg, an RRC connection request message) in an F1-AP initial uplink RRC message transfer message related to a non-UE. Thereafter, the procedure branches to a success situation 2110 and a failure situation 2130 .

According to success situation 2110, in step 2111, the central unit 110-2 transmits a UE context setup request message including a cause value. In step 2113, the distribution unit 110-1 allocates resources. Here, the resource may include a signaling radio bearer (SRB). In step 2115, the distribution unit 110-1 transmits a UE context setup response message including resource allocation information (eg, radio Resource Config Dedicated) for at least one data radio bearer. In step 2117, the central unit 110-2 transmits a downlink RRC message transfer message including an RRC connection establishment message. In step 2119, the distribution unit 110-1 transmits an RRC connection establishment message. In step 2121, the terminal 120 transmits an RRC connection establishment completion message. In step 2123, the distribution unit 110-1 transmits an RRC message, that is, an uplink RRC message delivery message including an RRC connection setup complete message to the central unit 110-2.

According to failure situation 2130, in step 2131, the central unit 110-2 transmits a UE context establishment request message including a cause value. In step 2133, the distribution unit 110-1 fails to allocate resources. That is, the distribution unit 110-1 determines that the terminal 120 cannot be accommodated. In step 2135, the distribution unit 110-1 transmits a UE context setup failure message. In step 2137, the central unit 110-2 transmits a downlink RRC message transfer message including an RRC connection reject message. In step 2139, the distribution unit 110-1 transmits an RRC connection reject message to the terminal 120.

Methods according to the embodiments described in the claims or specification of the present disclosure may be implemented in the form of hardware, software, or a combination of hardware and software.

When implemented in software, a computer readable storage medium storing one or more programs (software modules) may be provided. One or more programs stored in a computer-readable storage medium are configured for execution by one or more processors in an electronic device. The one or more programs include instructions that cause the electronic device to execute methods according to embodiments described in the claims or specification of the present disclosure.

Such programs (software modules, software) may include random access memory, non-volatile memory including flash memory, read only memory (ROM), and electrically erasable programmable ROM. (electrically erasable programmable read only memory (EEPROM), magnetic disc storage device, compact disc-ROM (CD-ROM), digital versatile discs (DVDs), or other It can be stored on optical storage devices, magnetic cassettes. Alternatively, it may be stored in a memory composed of a combination of some or all of these. In addition, each configuration memory may be included in multiple numbers.

In addition, the program is provided through a communication network such as the Internet, an intranet, a local area network (LAN), a wide area network (WAN), or a storage area network (SAN), or a communication network consisting of a combination thereof. It can be stored on an attachable storage device that can be accessed. Such a storage device may be connected to a device performing an embodiment of the present disclosure through an external port. In addition, a separate storage device on a communication network may be connected to a device performing an embodiment of the present disclosure.

In the specific embodiments of the present disclosure described above, components included in the disclosure are expressed in singular or plural numbers according to the specific embodiments presented. However, the singular or plural expressions are selected appropriately for the presented situation for convenience of explanation, and the present disclosure is not limited to singular or plural components, and even components expressed in plural are composed of the singular number or singular. Even the expressed components may be composed of a plurality.

Meanwhile, in the detailed description of the present disclosure, specific embodiments have been described, but various modifications are possible without departing from the scope of the present disclosure. Therefore, the scope of the present disclosure should not be limited to the described embodiments and should not be defined by the scope of the claims described below as well as those equivalent to the scope of these claims.

Claims (20)

In a method performed by a distributed unit (DU) of a base station in a wireless communication system,
Receiving a radio resource control (RRC) message including a resume request from a terminal; and
determining whether the resume request of the terminal is acceptable;
If the resumption request of the terminal is acceptable in the DU,
An initial uplink RRC message transfer message including an information element indicating to the central unit (CU) that the resume request of the UE in the DU is acceptable Transmitting an initial uplink RRC message transfer message doing;
Receiving a UE context setup request message including information related to a data radio bearer (DRB) from the CU; and
Transmitting to the CU a UE context setup response message including setting of the DRB based on the DRB-related information;
If the resumption request of the terminal is not acceptable in the DU,
Transmitting an initial uplink RRC transfer message not including the information element to the CU; and
Receiving a downlink RRC message transfer message including a rejection message of the resume request from the CU;
the information element comprises an RRC container;
The initial uplink RRC message transfer message includes a cell identifier and a DU user equipment F1 application identity (DU UE F1AP ID) indicating an identifier of the terminal through an F1 interface in the DU.
The method of claim 1,
The RRC message indicates a transition from an RRC inactive state to an RRC connected state,
The method for requesting resumption by the RRC message is an RRC connection resumption request procedure.
The method of claim 1,
Whether or not the resume request of the UE is acceptable is determined based on resource allocation of a media access control (MAC) layer and a physical (PHY) layer for a signaling radio bearer (SRB) in the DU. , method.
The method of claim 1,
The initial uplink RRC message transfer message,
Further comprising information about a cell radio network temporary identifier (C-RNTI) of the terminal.
In a method performed by a central unit (CU) of a base station in a wireless communication system,
Receiving a radio resource control (RRC) message including a resume request from a distributed unit (DU);
If an information element indicating that the resumption request of the UE is acceptable in the DU is not included in the initial uplink RRC message transfer message,
identifying that the resume request of the terminal is not acceptable in the DU; and
Transmitting a downlink RRC message transfer message including a rejection message of the resume request to the DU,
When an information element indicating that the resumption request of the UE is acceptable in the DU is included in an initial uplink RRC message transfer message,
Transmitting a UE context setup request message including data radio bearer (DRB) related information to the DU; and
Receiving a UE context setup response message including setting of the DRB based on the DRB-related information from the DU;
the information element comprises an RRC container;
The initial uplink RRC message transfer message includes a cell identifier and a DU user equipment F1 application identity (DU UE F1AP ID) indicating an identifier of the terminal through an F1 interface in the DU.
The method of claim 5,
The RRC message indicates a transition from an RRC inactive state to an RRC connected state,
The method for requesting resumption by the RRC message is an RRC connection resumption request procedure.
The method of claim 5,
Whether or not the resume request of the UE is acceptable is determined based on resource allocation of a media access control (MAC) layer and a physical (PHY) layer for a signaling radio bearer (SRB) in the DU. , method.
The method of claim 5,
The initial uplink RRC message transfer message,
Further comprising information about a cell radio network temporary identifier (C-RNTI) of the terminal.
In a distributed unit (DU) device of a base station of a wireless communication system,
transceiver;
Includes at least one processor coupled to the transceiver,
The at least one processor,
Receiving a radio resource control (RRC) message including a resume request from a terminal, determining whether the resume request of the terminal is acceptable,
When the resume request of the UE is acceptable in the DU, an information element indicating to a central unit (CU) that the resume request of the UE is acceptable in the DU Initial uplink including an information element Transmitting an RRC message transfer message (initial uplink RRC message transfer message), receiving a UE context setup request message including data radio bearer (DRB) related information from the CU, Sending a UE context setup response message including setting of the DRB based on the DRB-related information to the CU;
If the resumption request of the UE is not acceptable in the DU, sending an initial uplink RRC transfer message not including the information element to the CU, and including a rejection message of the resumption request from the CU Downlink Receive a downlink RRC message transfer message,
the information element comprises an RRC container;
The initial uplink RRC message transfer message includes a cell identifier and a DU user equipment F1 application identity (DU UE F1AP ID) indicating an identifier of the terminal through an F1 interface in the DU.
The method of claim 9,
The RRC message indicates a transition from an RRC inactive state to an RRC connected state,
The procedure for requesting resumption by the RRC message is an RRC connection resumption request procedure.
The method of claim 9,
Whether or not the resume request of the UE is acceptable is determined based on resource allocation of a media access control (MAC) layer and a physical (PHY) layer for a signaling radio bearer (SRB) in the DU. , Device.
The method of claim 9,
The initial uplink RRC message transfer message,
Further comprising information about a cell radio network temporary identifier (C-RNTI) of the terminal.
In a central unit (CU) device of a base station of a wireless communication system,
transceiver;
Includes at least one processor coupled to the transceiver,
The at least one processor,
Receiving a radio resource control (RRC) message including a resume request from a distributed unit (DU);
If an information element indicating that the resumption request of the UE is acceptable in the DU is not included in the initial uplink RRC message transfer message, the resumption request of the UE Identifying that the DU is unacceptable, and sending a downlink RRC message transfer message including a rejection message of the resume request to the DU,
When an information element indicating that the resumption request of the UE is acceptable in the DU is included in an initial uplink RRC message transfer message, the data radio bearer (data A UE context setup request message including radio bearer (DRB) related information is transmitted, and a UE context setup response message (UE context setup request message) including setting of the DRB based on the DRB related information from the DU receive the setup response message),
the information element comprises an RRC container;
The initial uplink RRC message transfer message includes a cell identifier and a DU user equipment F1 application identity (DU UE F1AP ID) indicating an identifier of the terminal through an F1 interface in the DU.
The method of claim 13,
The RRC message indicates a transition from an RRC inactive state to an RRC connected state,
The procedure for requesting resumption by the RRC message is an RRC connection resumption request procedure.
The method of claim 13,
Whether or not the resume request of the UE is acceptable is determined based on resource allocation of a media access control (MAC) layer and a physical (PHY) layer for a signaling radio bearer (SRB) in the DU. , Device.
The method of claim 13,
The initial uplink RRC message transfer message,
Further comprising information about a cell radio network temporary identifier (C-RNTI) of the terminal. delete delete delete delete

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